Mussel Feeding Research Articles

Monitoring of Dinophysis species and diarrhetic shellfish toxins in Flødevigen Bay, Norway: inter-annual variability over a 25-year time-series

The accumulation of phycotoxins in bivalve mussels associated with mussels feeding on toxic phytoplankton is a well-known phenomenon in Norway. Regular monitoring for 25 years has revealed that accumulation of Diarrhetic Shellfish poisoning (DSP) toxins in mussels is the main phycotoxin problem along the Norwegian coast. The aim of this study was to evaluate possible trends over time of Dinophysis spp. and DSP as well as possible correlation between abundance of Dinophysis spp. and toxin accumulation in mussels, as based on intensive and regular monitoring at the southern coast of Norway at Flødevigen Bay. The main source organism causing a risk of DSP in Norway is Dinophysis acuta. However, it cannot be excluded that other Dinophysis spp., e.g. D. acuminata and D. norvegica, may contribute to the total accumulation of toxins. The variability in the occurrence of these species is high at both short- and long-term; between days and between years. There are, however, some important overall patterns in the occurrence of the species during the last decades. Dinophysis acuminata and D. norvegica have mainly been abundant from March to December, whereas D. acuta has typically occurred in late summer and autumn (August–December). For all three species we have observed a narrowing of the peak season since 2002 at the same time as they have become less abundant. Coincident with these changes, the problem of the accumulation of DSP toxins in mussels along the southern coast of Norway has declined significantly, but it is still mainly restricted to the autumn. Why the cell concentration of Dinophysis spp. has declined after 2002 is not obvious, but this has occurred in a period with relatively high summer temperatures. The relatively simultaneous changes in physical, chemical and biological factors of the pelagic ecosystem along the southern coast of Norway indicate that complicated ecological interactions may be involved.

Grazing impacts of the invasive bivalve Limnoperna fortunei (Dunker, 1857) on single-celled, colonial and filamentous cyanobacteria

Feeding behavior of the invasive bivalve Limnoperna fortunei in the presence of single-celled, colonial, and filamentous cyanobacteria was tested in laboratory experiments to evaluate the effects of size and shape on mussel feeding. The first hypothesis holds that golden mussel filters more efficiently smaller particles, such as single cells of Microcystis, which could be more easily assimilated by its filtering apparatus. The second hypothesis sustains that L. fortunei filters more efficiently rounded colonies, such as Microcystis, which would be more easily ingested than lengthy filamentous, such as Planktothrix. Filtration rates of golden mussel in the presence of single-celled, colonial and filamentous cyanobacteria were similar. Nevertheless, there was a great difference in the ingestion and pseudofeces production rates. Single cells were widely accepted as food, while filamentous and colonial cyanobacteria were massively expelled as pseudofeces. The results confirmed the first hypothesis that golden mussel prefers to ingest smaller particles. The second hypothesis was rejected since filamentous were preferentially ingested than colonial cyanobacteria. Golden mussel has the potential to remove toxic cells (Microcystis), however this potential would be reduced in cyanobacteria blooms, where colonial forms which are preferentially rejected by L. fortunei, are predominant. In this case, the presence of this invasive bivalve could also enhance the occurrence of blooms by rejecting colonial and filamentous cyanobacteria in pseudofeces.

Tributary discharge, lake circulation and lake biology as drivers of water quality in the Canadian Nearshore of Lake Ontario

A combination of data from shipboard and deployed sensors, nutrient and major ion concentration data, and tributary discharge and current data was used to assess water quality patterns on the Canadian nearshore of Lake Ontario in 2008 and the factors that impact these patterns. Mixing areas at tributary mouths were characterized by high spatial and temporal variability in water quality. Conductivity at sensors offshore from tributaries was variably correlated with discharge, with the correspondence most evident during high spring flow. Tracers of land runoff were positively correlated with tributary discharge at three of five study locations. The spatial distribution of water quality was strongly influenced by the predominating alongshore circulations, with gradients frequently observed parallel to the shoreline away from tributary mouths. Upwelling, evident from temperature bands along the coastline, periodically created onshore–offshore gradients in chlorophyll a and dissolved inorganic nitrogen. Lake whiting, starting in July, further enhanced the effect of upwelling by accentuating differences in water clarity, suspended solids, and ionic composition between surface and bottom strata. In general, turbidity decreased and water clarity increased with lake depth. Gradients in water clarity and chlorophyll a suggestive of dreissenid mussel feeding were uncommon. Interacting land- and lake-based factors contributed to heterogeneous water quality over the coastline of Lake Ontario highlighting needs for water resource assessment methods sensitive to the temporal and spatial scales of problems as well as the connectivity between the land and the lake.

Modelling mussel growth in ecosystems with low suspended matter loads using a Dynamic Energy Budget approach

The environmental and the economic importance of shellfish stimulated a great deal of studies on their physiology over the last decades, with many attempts to model their growth. The first models developed to simulate bivalve growth were predominantly based on the Scope For Growth ( SFG) paradigm. In the last years there has been a shift towards the Dynamic Energy Budget ( DEB) paradigm. The general objective of this work is contributing to the evaluation of different approaches to simulate bivalve growth in low seston waters by: (i) implementing a model to simulate mussel growth in low suspended matter ecosystems based on the DEB theory (Kooijman, S.A.L.M., 2000. Dynamic and energy mass budgets in biological systems, Cambridge University Press); (ii) comparing and discussing different approaches to simulate feeding processes, in the light of recently published works both on experimental physiology and physiology modeling; (iii) comparing and discussing results obtained with a model based on EMMY ( Scholten and Smaal, 1998). The model implemented allowed to successfully simulate mussel feeding and shell length growth in two different Galician Rias. Obtained results together with literature data suggest that modeling of bivalve feeding should incorporate physiologic feed-backs related with food digestibility. In spite of considerable advances in bivalve modeling a number of issues is yet to be resolved, with emphasis on the way food sources are represented and feeding processes formulated.

A comparison of scope for growth (SFG) and dynamic energy budget (DEB) models applied to the blue mussel ( Mytilus edulis)

Growth of Mytilus edulis was simulated using individual based models following both Scope For Growth (SFG) and Dynamic Energy Budget (DEB) approaches. These models were parameterized using independent studies and calibrated for each dataset by adjusting the half-saturation coefficient of the food ingestion function term, X K , a common parameter in both approaches related to feeding behavior. Auto-calibration was carried out using an optimization tool, which provides an objective way of tuning the model. Both approaches yielded similar performance, suggesting that although the basis for constructing the models is different, both can successfully reproduce M. edulis growth. The good performance of both models in different environments achieved by adjusting a single parameter, X K , highlights the potential of these models for (1) producing prospective analysis of mussel growth and (2) investigating mussel feeding response in different ecosystems. Finally, we emphasize that the convergence of two different modeling approaches via calibration of X K , indicates the importance of the feeding behavior and local trophic conditions for bivalve growth performance. Consequently, further investigations should be conducted to explore the relationship of X K to environmental variables and/or to the sophistication of the functional response to food availability with the final objective of creating a general model that can be applied to different ecosystems without the need for calibration.

Feeding behavior of the mussel Mytilus galloprovincialis (L.) in a Mediterranean estuary: A field study

The feeding behavior of the mussel Mytilus galloprovincialis was investigated in the field on top of a mussel raft in Alfacs Bay, NW Mediterranean Sea. The experiments were performed in November 2006 and February, April and July 2007 using a flow-through filter feeding device. Total particulate matter (TPM), particulate organic matter (POM) and particulate inorganic matter (PIM) were calculated for the bay water, as well as the feces and pseudofeces of the mussels. These were used with the biodeposition method to estimate several feeding-physiological parameters, such as the clearance rate (CR), rejection rate through pseudofeces production (RP), organic ingestion rate (OIR), absorption rate (AR) and absorption efficiency (AE). The results showed that the characteristics of available suspended matter for mussels in terms of particle concentration (TPM: mg/l) and organic content ( f defined as POM/TPM) ranged 1.03–2.30 mg/l, and 0.48 to 0.73 respectively throughout the study period. This indicates a rather stable feeding environment of low concentrations of high organic content particles despite the wide range of temperatures recorded (from 10 to 26 °C). However, a characteristic of such a variation pattern of particle suspension (TPM and f) was that short-term variations (in the course of days) covered the whole range of annual variation. Accordingly, physiological parameters characterizing both food acquisition and absorption in mussels were found to respond to short-term variations in food regime. Pseudofeces production in mussels was low (less than 5% in most cases) and they tended to reduce their clearance rate instead of increasing their pseudofeces production in response to rising particle concentration. The absorption efficiency was positively related to the organic content of the seston particles. There was also a positive correlation between clearance rate and absorption efficiency. The reduction of clearance, ingestion and absorption rates obtained in July highlights a negative influence of high water temperatures upon feeding and digestive processes of mussels.

Has the invasive round goby caused new links in Baltic food webs?

The Ponto-Caspian round goby (Neogobius melanostomus, Pallas 1814) most probably was established in the Gulf of Gdansk, Baltic Sea, in the late 1980’s and has since become one of the dominant species in the region. In this study we assess the role of round gobies as prey for two important fish species in the Gulf of Gdansk, cod (Gadus morhua) and perch (Perca fluviatilis). We compared their present diet with stomach analyses from the area prior the round goby establishment, as well as with diet analysis from Baltic regions where round gobies are absent. There were large differences in the diet between cods from the Gulf of Gdansk 2003–2006 compared to cods in earlier studies (1977–1981) from the Southern Baltic Sea. There were also large differences in cod and perch diets from areas with and without round goby. Presently, round goby constitutes the most important prey for medium sized cods in Gulf of Gdansk, and perch from the same area almost exclusively feed on gobiids. Stomach analysis, trophic level estimates, and stable isotope analyses all indicated that cod and perch in Gulf of Gdansk after the round goby establishment belonged to a similar trophic level. Beside round goby, no mussel feeding fish contributed much to the diet of cod or at all to the diet of perch. Thus, it is likely that round gobies constitute a new energetic pathway from mussels to top predators. However, due to the short time elapsed after round goby establishment, we can only speculate on the species future impacts on Baltic food webs.

Absorption efficiency of blue mussels ( Mytilus edulis and M. trossulus) feeding on Atlantic salmon ( Salmo salar) feed and fecal particulates: Implications for integrated multi-trophic aquaculture

Blue mussels ( Mytilus edulis and M. trossulus) are grown adjacent to Atlantic salmon ( Salmo salar) cages in some open-water, Integrated Multi-Trophic Aquaculture (IMTA) systems. Absorption efficiency (AE) data of salmon feed ‘fines’ or salmon feces consumed by blue mussels is limited, but is crucial for determining organic load delivery to secondary niches (e.g. deposit feeders placed under mussel rafts) and the efficiency of IMTA systems. This study aimed to investigate AE of salmon particulates relative to some commercial shellfish diets and potential effects of mussel size. In the laboratory trials, there were significant differences of fecal OC ( p = 0.00) across diets but no significant differences ( p = 0.07) of fecal OC between mussel size classes (30–35 mm, 50–55 mm and 70–75 mm lengths) fed the same diet. The AE of a commercial spat formula ( Phaeodactylum tricornutum, Chaetoceros-B, and Nanochloropsis oculata), a commercial diatom diet ( Thalassiosira weissflogeii), salmon feed, salmon feces, and total particulate matter (TPM) at salmon cages; averaged 87, 81, 90, 86, and 54%, respectively. TPM at a salmon cage increased with total organic matter ( r 2 = 0.76), but decreased in OC ( r 2 = 0.87), suggesting periods of substantial inorganic particle (e.g. silt) flux. Consequently, mean values of OC and AE of TPM at salmon cages was less than what would be expected if mussels were ingesting significant portions of salmon particulates. The results of this study emphasize the temporal/spatial variation of ‘particle plumes’ exiting fish cages is a major consideration for the placement of suspension or filter feeders at open-water IMTA sites. However, the AE data presented suggests that organic material in particulate salmon culture waste can effectively be utilized by blue mussels.

Effects of the suspension feeding musselMytilus trossuluson a brackish water macroalgal and associated invertebrate community

AbstractThe importance of suspension‐feeding mussels is particularly apparent in benthic communities; however, the role of this feeding strategy on the development of macroalgal and associated invertebrate communities is in general poorly known. The effect of suspension‐feeding musselsMytilus trossuluson benthic communities was studied in anin situfactorial field experiment in the Northern Baltic Sea over one ice‐free season. The experiment was performed under different regimes of wave exposure (low and moderate) and on different sedimentary habitats (soft bottom with high organic content, soft bottom with low organic content, and hard bottom). In general the presence of mussels was associated with increased biomass of filamentous algae, herbivores and deposit feeders and decreased biomass of charophytes. The effect ofM. trossulusinteracted with the effect of exposure and substrate. Stronger responses were observed in moderately exposed than in sheltered areas. The presence ofM. trossulusaffected charophytes and deposit feeders on sand with low content of organic matter and filamentous algae on pebbles but not on other substrate types. The magnitude of the effects varied between months. The results suggest that (i) even in dynamic coastal systems the biodeposits and excretions of mussels are at least partly assimilated locally and are not flushed away to the open sea, (ii) the accumulation of faecal material induced elevated growth of deposit feeders, (iii) mussels enhanced the growth of ephemeral macroalgae and reduced the growth of perennial macroalgae, and (iv) together with increasing benthic primary production, mussels indirectly increase the production of herbivores.

Mechanisms of invasion resistance: competition among intertidal mussels promotes establishment of invasive species and displacement of native species

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 383:187-197 (2009) - DOI: https://doi.org/10.3354/meps07982 Mechanisms of invasion resistance: competition among intertidal mussels promotes establishment of invasive species and displacement of native species J. S. Shinen1,*, S. G. Morgan2 1Estación Costera de Investigaciones Marinas, Departamento de Ecología, Pontificia Universidad Católica de Chile, Alameda 340, Santiago, Chile 2Bodega Marine Laboratory, Department of Environmental Science and Policy, University of California Davis, PO Box 247, Bodega Bay, California 94923, USA *Email: jlshinen@bio.puc.cl ABSTRACT: Understanding interactions between invasive species and recipient communities is essential to determining whether invasive species will become established and spread. In this study, we explored the role of competition and the specific mechanisms of interaction in limiting the spread of the Mediterranean bay mussel Mytilus galloprovincialis within a Pacific Northwest invasion front. We examined the role of direct (interference) and indirect (exploitation) mechanisms of competition among M. galloprovincialis and 2 native mussels (M. trossulus and M. californianus). As the fastest-growing organisms are often competitively dominant in space-limited systems, such as rocky intertidal communities, we used changes in relative performance (growth and survival) in monocultures and polycultures to assess interactions among mussels. Performance of M. galloprovincialis was always greater than that of the 2 native species of mussels in both field and laboratory manipulations of species composition and density, indicating that interspecific competition did not strongly limit the growth or survival of the invader. Moreover, the presence of M. galloprovincialis consistently led to both reduced growth and survival of M. trossulus. Laboratory studies of mussel feeding and behavior revealed M. galloprovincialis to be a robust interference competitor. The invader restricted movement, smothered and interfered with filter feeding of the 2 native species of mussels. Rather than limiting invasion, interference competition gave M. galloprovincialis a competitive advantage over the native mussels. Our results suggest M. galloprovincialis may have contributed to the displacement of M. trossulus along much of its historic southern range. KEY WORDS: Exploitation competition · Interference competition · Mytilus · Rocky intertidal communities Full text in pdf format PreviousNextCite this article as: Shinen JS, Morgan SG (2009) Mechanisms of invasion resistance: competition among intertidal mussels promotes establishment of invasive species and displacement of native species. Mar Ecol Prog Ser 383:187-197. https://doi.org/10.3354/meps07982 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 383. Online publication date: May 14, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Effect of mussel bio-pumping on the drag on and flow around a mussel crop rope

Drag measurements are conducted to determine if inhalant and exhalant of fluid during mussel feeding has a detectable influence on the drag of a mussel-encrusted rope such as is commonly used in suspended aquaculture. The experiment is conducted using an artificial mussel crop rope constructed using the shells of Perna canaliculus, with 100 mussels (mean shell length 83.4mm, S.D. 8.7mm) attached over a length of 0.90m. Fluid pumping from mussel feeding is simulated using inhalant and exhalant jets pumping at a rate of 7Lh−1 per mussel. The mussel rope is towed at speeds between 0.05 and 0.4ms−1. No significant difference is found between drag with and without the mussels pumping indicating that assessments of the drag on or from mussel long-lines may safely neglect the effect of mussel feeding. We suggest using twice the mussel shell size to define mussel rope diameter which gives a drag coefficient of CD ∼1.0. A value of CD ∼1.3 is obtained if the projected area of the mussel rope is used. Particle tracking velocimetry (PTV) is also used on a similar but shorter crop rope (0.3m length) in a recirculating flume which reveals that mussel pumping induces only small changes to mean velocity and turbulence distributions downstream of the rope. The wake of the crop rope is highly turbulent and dominated by shear instabilities formed in the free shear layer, similar to bluff body wakes. The sharp edges of the mussel shells provide many points for flow separation to occur. At typical ambient velocities, turbulent kinetic energy produced by the exhalant jets is small in comparison to that from flow around the crop rope.

Acute toxic effects of ionic liquids on zebra mussel (Dreissena polymorpha) survival and feeding

Ionic liquids (ILs) are being designed as green alternatives to volatile organic solvents that are currently used in a wide range of industrial processes. While knowledge about the toxicity of various ILs to aquatic organisms has expanded in recent years, toxicity data remains limited to a few animal taxa. Furthermore, few studies have examined the non-lethal effects of ILs on aquatic organisms. We investigated how ILs affect mortality and feeding of the zebra mussel (Dreissena polymorpha), a sessile bivalve that is invasive in North America and much of Europe. Lethal effects of six ILs (butyl-, hexyl-, or octyl-chains on either a methylpyridinium or methylimidazolium cationic base) were studied with 96 h acute bioassays. Filtering behavior was examined in 2 h feeding trials of individual mussels fed Chlamydomonas reinhardtii and exposed to sublethal concentrations of the three imidazolium-based ILs. The ILs tested caused acute mortality over a wide range of concentrations (LC50 = 21.4 to 1290 mg L−1), ILs with longer alkyl chains were more toxic, and pyridinium- and imidazolium-based ILs had similar toxicities. When comparing toxicity to the same IL across organisms, zebra mussels exhibit some of the highest LC50 values and would be among the most resistant aquatic organisms in the event of an IL release. Short-term exposure to any IL reduced zebra mussel feeding. For butyl- and hexyl-chain ILs, feeding was significantly reduced at the acute LC50, whereas the octyl-chain IL reduced feeding at the acute LC5. Reduced survival and feeding by zebra mussels in the presence of ILs could have substantial effects on other trophic levels, which could lead to changes to affected ecosystems that would not have been predicted solely from standard mortality bioassays. Based on our mortality data, ILs are no worse than currently used industrial solvents; however, results from our feeding experiments demonstrate the potential for significant effects at sublethal concentrations. Consequently, we suggest that more ecologically relevant endpoints should be incorporated into a thorough hazard assessment of ILs.

Feedback between zebra mussel selective feeding and algal composition affects mussel condition: did the regime changer pay a price for its success?

Summary1. We investigated the role of algal composition on pumping, clearance, assimilation, pseudofaeces and faeces production, feeding time budgets, and condition of zebra mussels from spring to autumn at two sites in Saginaw Bay (Lake Huron) and one site in western Lake Erie. Size‐fractioned chlorophyll was used to distinguish between feeding on small (<53 μm) and large (>53 μm) size fractions, and mussel feeding behaviour was quantified by video observations.2. Mussel pumping, clearance and assimilation rates varied among sites, particularly during summer, when phytoplankton composition varied considerably among sites. Lowest values were seen at the inner‐bay site of Saginaw Bay, low to moderate values at the outer‐bay site of Saginaw Bay, and high values at the Lake Erie site. Clearance, pumping and assimilation rates were all highly positively correlated (R2 = 0.76) with per cent contribution of flagellates to total algal biomass and negatively correlated with per cent of Microcystis aeruginosa (R2 = 0.63). The negative effects on pumping rate (as determined by clearance rate on the <53 μm fraction) of Microcystis, which occurred in the >53 μm fraction, could be mitigated by the presence of flagellates in the <53 μm fraction.3. Visual observations of mussel feeding showed evidence for poor seston quality during summer negatively affecting feeding rates. High faeces production during times of low assimilation rate was suggestive of poor assimilation efficiency and/or viable gut passage of grazing resistant algae. Long periods of time not filtering by the mussels during some Microcystis blooms and lack of production of a filtering current during one experiment were suggestive of intoxication from microcystin or other secondary compounds.4. Clearance and feeding rates of the mussels in Saginaw Bay were high during spring and autumn and very low in summer, particularly at the inner‐bay site. Condition of the mussels (mass : length ratio) was highest in spring and lowest during summer. This seasonal variation probably reflected high food assimilation rate during autumn and spring and low assimilation rate and reproduction during summer. The condition of mussels throughout the year was higher at the outer‐bay than the inner‐bay site, reflecting better feeding conditions at the former. Mussel selective feeding may have been responsible for the poor quality of food at the inner bay site; therefore, we postulate that a regime shift in phytoplankton composition promoted by the mussels fed back into lowered condition of the mussels.

Impact of suspended mussels (Mytilus edulis L.) on plankton communities in a Magdalen Islands lagoon (Québec, Canada): A mesocosm approach

The Grande-Entrée Lagoon (Magdalen Islands, Canada) has supported mussel ( Mytilus edulis) cultivation for the last 25 years. Algal biomass in this lagoon is relatively low while heterotrophic plankton biomass is high. Although often considered herbivorous, it is known that filter-feeding bivalves can consume various types of food, from bacteria to zooplankton. We hypothesize that along with phytoplankton, heterotrophs constitute an important food resource for the Grande-Entrée mussels. In situ mesocosm experiments were undertaken at different seasons using short socks filled with mussels from the same cohort taken from an aquaculture farm, in order to determine the impact of cultured mussels on local plankton communities and assess the role of heterotrophs. Filtration activity by the mussels and associated epibionts present in the socks was expressed as clearance rates (CR). The average CR over all taxa was lowest in June and highest in October. Diatoms, dinoflagellates and heterotrophic protists constituted the bulk of planktonic carbon removed by mussels. While smaller-sized taxa contributed little (< 5%) to mussel carbon intake, large-sized heterotrophs (namely ciliates) contributed 69 to 88%. Taxon-marker pigment analyses generally confirmed these observations for groups containing phototrophic pigments. The high heterotrophic biomass retained by mussels indicates they are a major food source for mussels in this environment and should be considered both in the evaluation of mussel feeding and in assessing the influence of cultured mussels on local plankton ecosystems.

Quantitative trends of zebra mussels in Lake Balaton (Hungary) in 2003–2005 at different water levels

During the extremely dry period between 2000 and 2003, the water level of Lake Balaton decreased by 82 cm and 80% of the stony littoral, an important habitat for the zebra mussel (Dreissena polymorpha), became dry. A recovery period started in 2004 due to intense precipitation, which increased water levels in the lake. Seasonal and spatial variations of the relative abundance, population density, population structure and biomass of the zebra mussel and the relative abundance of the amphipod Chelicorophium curvispinum were monitored in the period of 2003–2005 at four different shoreline sections and in two different portions (on the bottom and near the surface portion of the rip-rap) of Lake Balaton. Along with these studies, a quantitative survey of mussel larvae found in the plankton and of the abundance of mussel feeding diving ducks were made. As a consequence of the water level fall, on the dried part of the stony littoral, numerous zebra mussel druses perished. Following the dry period in early 2004, the relative abundance of the mussel on the bottom stones was smaller than in 2003 and the bottom community was dominated by C. curvispinum. By the end of 2004 and during 2005, the water level returned to normal and the surfaces of the reinundated stones were conducive to the successful colonization of zebra mussels. Hence, they returned as the dominant fauna in 2005. The stones near the surface might provide a new substrate for the recruitment of zebra mussels, probably offering more suitable substrata for the settlement in 2005 than in 2003. Therefore, the new substrata available in 2005 may have encouraged better and more rapid zebra mussel colonization than before. Zebra mussels may be better competitors for new space than C. curvispinum. A minor change of water-level fluctuation in 2005 and the reduction in population size of the mussel feeding waterfowl could have contributed to the intensive spread of zebra mussel by 2005.

Density-dependent effects of a new invasive false mussel, Mytilopsis trautwineana (Tryon 1866), on shrimp, Litopenaeus vannamei (Boone 1931), aquaculture in Colombia

Dreissenid and mytilid bivalve molluscs have become some of the most important invasive pests in the world's marine, brackish and fresh water ecosystems. We report on a newly invasive dressenid false mussel, Mytilopsis trautwineana, within a shrimp farm on the Caribbean coast of Colombia. The impacts of the mussel and the response of the shrimps can be explained through density-dependent interactions. A low density of filter feeding mussels has a positive effect on aquaculture through the removal of suspended particulate matter. However, at high densities mussels reduce shrimp survival from 76.0 ± 2.1% to 61.2 ± 2.3%. The economic impact of reduced shrimp survival is somewhat mediated through density-dependent responses in the form of compensatory growth, with shrimps attaining a higher mean weight and higher food conversion ratio. Despite these responses, it is estimated that fouling by M. trautwineana costs US$9000 ha − 1 yr − 1 . The causes of reduced shrimp productivity are both direct and indirect. Mussels displace the shrimps from the food-rich pond bed. Mussel filtration increases water clarity, which in turn exposes shrimps to enhanced predation from birds. Shrimps respond to clearer water by reducing pigmentation, which reduces their commercial value. Mussels also foul aeration devices, significantly reducing their ability to maintain favourable DO 2 levels. The apparent salinity tolerance of M. trautwineana suggests the species will become a more widespread biofouling nuisance. Possible control strategies include changes to management procedures, chemical treatments, microencapsulated BioBullets, polyculture with omnivorous fishes, or encouragement of indigenous mangrove-dwelling grapsid crabs.

Differential grazer‐mediated effects of high summer temperatures on pico‐ and nanoplankton communities

We investigated the role of a macrograzer (the filter feeding mussel Dreissena polymorpha) in mediating effects of high summer temperatures on the dominant components of natural river plankton (i.e., bacteria, algae, and heterotrophic flagellates) in flow channel experiments. Effects of adaptation (by comparing mussels from a southern and a northern population) and thermal acclimation of the mussels were considered. Both heterotrophic flagellates and algae are released from grazing pressure and increase in abundance at temperatures above 20°C. Bacterial abundance, however, decreased with increasing temperature, suggesting a trophic cascade (mussel‐flagellates‐bacteria) that is altered by the temperature response of the mussel ingestion rate. Warm acclimation of the mussels did not change the outcome of the experiments. The dreissenids from the southern population showed a significantly higher ingestion rate than those from the northern population only in July. The general pattern (i.e., decreasing ingestion rates at high temperatures) was found in both populations. Microbial communities controlled by macrofauna can experience substantial changes in warm summers because of differential development of direct and indirect grazing effects with increasing temperature.

In situ mussel feeding behavior in relation to multiple environmental factors: Regulation through food concentration and tidal conditions

Feeding behavior of mussels (Mytilus edulis) was measured in situ using a video camera and expressed as the mean percentage of valve gape aperture (VA), concomitant with environmental and biological parameters over two tidal cycles. Mussel feeding behavior and the physical parameters responded to three primary tidal components, of which semidiurnal was dominant (12.42 h). VA was synchronized with chlorophyll a (Chl a) concentration (proxy for food) with a strong positive correlation (r = 0.72, p &lt; 0.001). Chl a and suspended particulate matter (SPM) were dependent on tidal advection. The combination of the reconstructed tidal constituents derived from harmonic analysis were used to successfully model mussel feeding behavior (r = 0.90, p &lt; 0.001). In this concentration range (0.6 to 2.5 µg L−1), Chl a, measured at 1 m above the mussel bed, regulates mussel feeding behavior irrespective of the presence of predators, changes in SPM, or flow velocity.

Hydrodynamic Forcing of Long-Line Mussel Farms: Observations

The first detailed observations of the motion and loading of a mussel (shellfish) aquaculture long-line are described in order to identify the dominant modes of flow-structure interaction and provide a baseline for prediction of future structures. A long-line is typically a 120m long sequence of surface floats beneath which is looped rope bearing the mussel crop. Accelerometer and load cell data from sensors mounted on the structure along with remote radar data are examined in the context of wave and current measurements. The mussels comprise the largest mass and drag element of the structure, and the tidally affected pretensioning of the mooring lines dominates the background load. However, waves and currents increase the maximum load by potentially 100% over this value. The floats at each end of the long-line follow the wave orbital motion reasonably well, more so than the floats in the middle of the backbone. The mussel-laden loops of rope (droppers) clearly respond differently to the floats, implying flexibility in the vertical dimension. This suggests that flow around the droppers, which influences mussel feeding ability and hence production, is complex and highly three-dimensional.

Variation in scope for growth: a test of food limitation among intertidal mussels

Wellington Harbour supports large populations of the mussels Aulacomya maoriana, Mytilus galloprovincialis and Perna canaliculus that are almost entirely absent from nearby coastal locations in Cook Strait. We calculated scope for growth (SFG) using ambient Cook Strait water over a broad temporal scale and a broad range of seston conditions to determine if negative SFG explains this phenomenon. Although all three mussel species had positive mean SFG values, variation in SFG was high and negative values often occurred: A. maoriana 19.1 J g−1 h−1, 43% of mussels showed negative SFG; M. galloprovincialis 1.26, 52% negative SFG; P. canaliculus 45.6, 27% negative SFG. Negative SFG was most often due to negative absorption efficiency caused by metabolic faecal loss that is characteristic of mussels feeding in environments with low seston quality. From our ecophysiology data we constructed a model to estimate SFG based on physiological responses to the narrow range of seston conditions typical of Cook Strait (Model One), and a model to estimate SFG based on physiological responses of mussels to the broad range of seston conditions typical of Wellington Harbour and Cook Strait (Model Two). We used seston data collected over an 18-month period from sites in Wellington Harbour and Cook Strait to derive 159 estimates of species-specific mussel SFG from both models. Both models produced higher estimates of SFG for mussels in the Harbour compared with those at Cook Strait sites. This was consistent with elevated particulate concentrations in the Harbour than at Cook Strait sites, and in agreement with previous studies. For Cook Strait mussels, both models produced negative estimates of net energy balance for long periods of time (several months), whereas for Harbour mussels negative SFG estimates were generally short in duration. We conclude that our short-term laboratory-based determinations of SFG and our long-term bioenergetics modelling estimates do not conclusively support the hypothesis of food limitation for three coexisting taxa of mussels in the intertidal region of Cook Strait, New Zealand.